Pineal cyst with haemorrhage
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Cystic pineal lesion with blood/fluid level. No solid nodular enhancement.
This patient went on to have a biopsy/drainage of the cyst.
Sections show a single fragment of glial tissue lined by ependymal cells. The reactive changes include fibrillary astrocytes and frequent Rosenthal fibers. Some infiltration by macrophages and lymphocytes as identified by H & E stain and immunohistochemistry (HAM-56 and LCA respectively). Immunohistochemistry reveals strong positivity of the astrocytes for GFAP (glial fibrillary acidic protein). There are some cells showing nuclear positivity for MIB-1. Immunohistochemistry for phosphorylated neurofilaments reveal very rare linear axon-like structures. Iron stain shows that many of the above-mentioned macrophages contain hemosiderin granules.
Ependymal-lined glial tissue with fibrillary astrocytes, Rosenthal fibers, macrophages, and occasional lymphocytes
The histologic findings of the small biopsy are consistent with fibrillary gliosis of subependymal tissue adjacent to a lesion. However, given the anatomic location of the lesion, the differential diagnosis would also include, but would not be limited to, the glial component of a pineal cyst and a pilocytic astrocytoma. The small biopsy size precludes a definitive diagnosis in this regard.